Survey of MicrobesSurvey of MicrobesPart I: Important Part I: Important

prokaryotesprokaryotes

But first… a word on shape, But first… a word on shape, arrangement and sizearrangement and size

SHAPES:1. ____________ – spherical, ball shaped2. ____________ - rod3. _________________– helical, comma (vibrio),

twisted rod (spirillum, rigid with lophotrichous flagella), spirochete (flexible with periplasmic flagella)

Also… intermediate shapes like coccobacillus cells can be thin (filamentous) Cells can be pleomorphic (species can have >1

form such as Corynebacterium diphtheriae)

arrangements of bacteria

Pairs (2 like diplococci, diplobacilli)Tetrads (4 cells in packet)Sarcinae (balls or blocks of 8, 16, 32 cells)Chains (streptococci; streptobacilli)Clusters (Micrococcus, Staphylococcus)Palisades arrangement (Corynebacteria)

streptococci diplobacillus spirochete spirillum

sizesize

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Bacterial Taxonomy Based on Bacterial Taxonomy Based on Bergey’s ManualBergey’s Manual

Bergey’s Manual of Determinative Bacteriology – five volume resource covering all known prokaryotes◦Classification based on genetic information –phylogenetic

◦Two domains: Archaea and Bacteria◦Five major subgroups with 25 different phyla

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Major Taxonomic Groups of BacteriaMajor Taxonomic Groups of Bacteria

Domain ____________ – primitive, adapted to extreme habitats and modes of nutrition

Domain Bacteria:◦Phylum Proteobacteria – Gram-negative cell

walls◦Phylum Firmicutes – mainly gram-positive with

low G + C content ◦Phylum Actinobacteria – Gram-positive with high

G + C content

Figure 4.27 Universal phylogenetic Figure 4.27 Universal phylogenetic treetree

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IMPORTANT GRAM IMPORTANT GRAM POSITIVE BACTERIAPOSITIVE BACTERIA

Soil bacteria: •Bacillus •Clostridium (some pathogens)

Lactic acid bacteria: Lactococcus, Lactobacillus, Acidophilus

Several human pathogens:•Staphylococcus (S. aureus) •Streptococcus (S. pyogenes, S. pneumoniae)•Mycobacterium (M. leprae and M. tuberculosis)•Corynebacterium •Listeria monocytogenes

Others:•Propionibacterium •Streptomyces•Mycoplasma! (no cell wall, but it’s grouped with G+)

Important Gram positive Important Gram positive bacteriabacteria

StaphylococcusStaphylococcusGenus: staphylo=“grape clusters”S. epidermidis – opportunistic pathogen;

no virulence factors; natural floraS. aureus – hemolytic, coagulase,

invasive; flora of the nose but still a pathogen

Many diseases: endocarditis, pneumonia, meningitis, arthritis, intoxications such as ______________________ and food poisoning; more often cuteneous: ◦pimples/boils/abscesses/carbuncles, pink eye◦scalded skin syndrome, ◦impetigo.

1a.) Gram + cocci

BOIL

CARBUNCLE

SCALDED SKIN SYNDROME

IMPETIGO

Strep. pyogenes?

Endocarditis

Virulence factors of StaphVirulence factors of Staph

Pathogenic effects: mostly associated with ________________________

• Diagnostic marker• localized clotting

Prevents bacteria frombeing clearedfrom host

• Kills leukocytes so that bacteria are not phagocytosed

• Form pus and acne

1a.) Gram + cocci--Staph

Current estimate:>60% of hospitalacquired S. aureusinfections are MRSA

Many strains are MDR!!

TSN, The Surveillance Network (data include hospital infections); NNIS, National Nosocomial Infections Surveillance System (data include only intensive care units); SENTRY, includes only skin and soft tissue infections.

Percentage of Staphylococcus aureus isolates resistant to methicillin in national surveys, United States, 1999–2004.

(source: Klein et al. 2007. EID)

Hospitalizations and Deaths Caused by Methicillin-Resistant Staphylococcus aureus, United States, 1999–2005

Figure 1. Estimated methicillin-resistant Staphylococcus aureus (MRSA)–related hospitalization rates, United States, 1999–2005. Rates are no. MRSA-related discharges/1,000 hospitalizations. Error bars represent 95% confidence intervals. (source: Klein et al. 2007. EID)

StreptococcusStreptococcus

1. Group A Strep = ____________ Strep throat, pharyngitis

◦ Secondary: Scarlet fever (systemic rash); Rheumatic fever (heart valves, arthritis)

Cuteneous infections: Impetigo (older children), pyoderma, acne, Erysipelas – AKA “St. Anthony’s Fire”; Toxic shock syndrome

◦ ____________ ____________ ; “flesh eating bacteria” All are mediated by various virulence factors

– esp. ____________

1a.) Gram + cocci

Strawberry tongue – Scarlet fever

Strep throat

1a.) Gram + cocci--Strep

StreptococcusStreptococcus

Streptococcal toxic shock syndrome (STSS), causes blood pressure to drop rapidly and various organs to fail. About 20% of patients with necrotizing fasciitis and more than half of those with STSS will die. Generally, the mortality rate for other forms of invasive group A streptococcal disease is 10-15%.

1a.) Gram + cocci--Strep

PYODERMA (S. aureus or S. pyogenes)

Virulence factors of StrepVirulence factors of Strep

____________ : due to secretion of many enzymes and toxins including:

◦____________ : lyse red blood cells◦____________ : breaks down collagen (cement of

connective tissue: helps organism spread)

1a.) Gram + cocci--Strep

Other pathogenic Other pathogenic StreptococciStreptococci• ________________________ : causes dental caries (cavities)

• ____________________________ (often called pneumococcus)• carried in upper respiratory tract and nasopharynx of humans

15% of children and 5% of adults are “carriers” • grow in pairs (NOT in long chains)• most common cause of pneumonia and otitis media (middle ear infection)

1a.) Gram + cocci--Strep

ClostridiumClostridium

____________ ____________ (cannot grow in oxygen) rod shaped bacteriacontain ____________ : resistant to heat and

chemicals; spores are introduced into injury or anaerobic wound or ingested (botulism)◦ spores germinate and active bacteria multiply

1b.) Gram + rods--Clostridium

Medically important Medically important speciesspeciesC. tetani: ____________

◦neurotoxin: called tetanospasmin (a dot the size of a period-kills 30!)

◦blocks muscles relaxation: muscles spasm and contract◦contractions: tear muscles/cause compression fraction

of vertebrae death from spasms of respiratory muscles vaccine (DPT): inactivated toxin used to stimulate antibodies

C. difficile: ____________ ____________ often caused when antibiotic therapy alters microflora in intestines and allows for growth of this organism

C. perfringens: causes ______________________ (severe tissue death); also foodborne diarrhea

1b.) Gram + rods--Clostridium

Medically important speciesMedically important speciesC. botulinum: ____________________ .grows in anaerobic environments (canned foods): discard

bulging cans! Produces toxin: MOST potent of ALL toxins: specific for nerve

endings (synapses) Blocks acetylcholine (neurotransmitter): nerve impulses

blocked! Botulism disease progression: Initial symptom: blurred vision and nausea flaccid

paralysis: respiratory and cardiac failure slow recovery: nerve endings regenerate; respiratory support:

antibiotics are of no use! Prevention: Toxin is destroyed by boiling and nitrites in food

prevent bacterial growth A word about commercial use of BOTOX:

◦ prevent wrinkles – maybe, BUT…◦ strasbismus: crossed eyes◦ blephorospasm: inability to keep eyelids open

BacillusBacilluscommonly found in soil produces ____________

Medically important species of Bacillus

• ____________________ : anthrax disease of cattle, sheep and humans Two forms of anthrax:

•____________(skin): transmitted through a break in the skincause pustule or lesions: tissue dies, crusts and falls offsystemic (bloodstream): shock/ collapse

•____________(pulmonary): transmitted by inhaling anthrax spores starts as pneumonia, high fever then septicemia, respiratory

distress, death

•biowarfare agent: spores can be spread in aerosols•no spread from person to person!•penicillin effective if given early

Anthrax sepsis due to inhalation anthrax (now involving eye)Woman was exposed to animal hides; Pennsylvania 2006

Cutaneous anthrax – note BLACK lesions

Inhalation anthrax on x-ray;Patient died next day.

Bacillus (cont’d)Bacillus (cont’d)

Bacillus ____________ : food poisoning often from starchy food especially rice

Bacillus thuringiensis: insect pathogen produces delta endotoxin in crystal form insect eats toxin crystals and dies ◦ sold for plant treatment as pesticide ◦ transgenic plants engineered to produce toxin

Bacillus subtilis: produces bacitracin

Bacillus polymyxa: produce polymixin

1b.) Gram + rods--Bacillus

MycobacteriumMycobacterium____________________________________ Acid-fast stain – mycolic acid; Slow growing1. Leprosy: mainly affects the skin, peripheral

nerves, upper respiratory tract. ◦ discovered by G.A. Hansen in 1873; first bacterium to be

identified as causing disease in man.

◦ contagious, but not widespread because 95% of the population have competent immune systems.

2. TB: causes tubercles in lungs, bones; poor health, crowding plays a role (communicable);

◦ leading cause of death in the world from a single infectious disease!

◦ affects 1.7 billion people/year which is equal to one-third of the entire world population!

1b.) Gram + rodsMycobacterium

TB – cavitation, and calcified tubercle

Other pathogensOther pathogens

1. ___________________ - C. diphtheriae: causes diphtheria – DPT vaccine

-pseudomembrane on tonsils-strong toxin – can destroy heart

2. ______________________– food poisoning; outbreak in hot dogs; intracellular pathogen

1b.) Gram + rods--others

Pallisades arrangement of Corynebacterium

Can be pleiomorphic

Pseudomembrane:necrosis, plasma, fibrin and bacteria

Nonpathogenic, but important!Nonpathogenic, but important!

1. Propionibacterium, Brevibacterium - swiss cheese, bacterial acne, stinky feet; propionic acid and sulfur compounds

2. Streptomyces - antibiotic production: erythromycin, neomycin, streptomycin,

tetracycline

3. ____________– normal flora in gut and vagina

◦ found in yogurt, cheeses (mozzarella, cheddar, provolone)

________________________

naturally lack a cell wallstabilized by sterols,

resistant to lysisextremely small (0.1 – 0.5 µm)range in shape from filamentous to coccus or

doughnut shaped____________ ____________ Mycoplasma ____________ – atypical

pneumonia in humans (“walking pneumonia”)